diff --git a/src/iterative.rs b/src/iterative.rs
index ca068a9..7d35233 100644
--- a/src/iterative.rs
+++ b/src/iterative.rs
@@ -181,6 +181,39 @@ impl<T: Ord> BinarySearchTree<T> for IterativeBST<T> {
             self.size += 1;
         }
     }
+    
+    ///Inserts the given value as a node or updates an existing node with the same value.
+    ///
+    /// If a node with the given value already exists, the provided function `f` is called
+    /// with a mutable reference to the existing value to update it.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use bst_rs::{BinarySearchTree, RecursiveBST};
+    ///
+    /// let mut bst = RecursiveBST::new();
+    ///
+    /// bst.insert((1, 10));
+    /// assert_eq!(bst.retrieve(&(1, 10)), Some(&(1, 10)));
+    ///
+    /// bst.insert_or_update((1, 10), |tuple| tuple.1 = 30);
+    /// assert_eq!(bst.retrieve(&(1, 10)), None);
+    /// assert_eq!(bst.retrieve(&(1, 30)), Some(&(1, 30)));
+    ///
+    /// bst.insert_or_update((2, 20), |_| {});
+    /// assert_eq!(bst.size(), 2);
+    /// ```
+    fn insert_or_update<F>(&mut self, value: T, f: F)
+        where
+            F: Fn(&mut T) {
+        if let Ok(inserted) = Node::iterative_insert_or_update(&mut self.root, value, f) {
+            if inserted {
+                self.size += 1;
+            }
+        } 
+    }
+
 
     /// Returns `true` if the binary search tree contains an element with the given value.
     ///
@@ -1588,4 +1621,30 @@ mod tests {
 
         assert_eq!(actual_bst, expected_bst);
     }
+
+    #[test]
+    fn successfully_insert_or_update_elements() {
+        let mut bst = IterativeBST::new();
+        
+        bst.insert((1, 10));
+        bst.insert((2, 20));
+        bst.insert((3, 30));
+        assert_eq!(bst.size(), 3);
+        
+        bst.insert_or_update((1, 50), |pair| pair.1 = 15);
+        assert_eq!(bst.retrieve(&(1, 50)), Some(&(1, 50)));
+        bst.insert_or_update((1, 50), |pair| pair.1 = 15);
+        assert_eq!(bst.retrieve(&(1, 50)), None); 
+        println!("{}", bst);
+        assert_eq!(bst.size(), 4);
+
+        bst.insert_or_update((4, 40), |_| {});
+        assert_eq!(bst.size(), 5);
+        
+        bst.insert_or_update((4, 40), |pair| {
+            pair.1 *= 2;
+        });
+        assert_eq!(bst.retrieve(&(4, 40)), None);
+        assert_eq!(bst.retrieve(&(4, 80)), Some(&(4, 80)));
+    }
 }
diff --git a/src/lib.rs b/src/lib.rs
index e31dad4..30af7bf 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -244,6 +244,13 @@ pub trait BinarySearchTree<T: Ord> {
     /// **Duplicate values are _not allowed_**.
     fn insert(&mut self, value: T);
 
+    /// Inserts given value as a node or updates T with some function
+    /// 
+    /// **Duplicate values are allowed**.
+    fn insert_or_update<F>(&mut self, value: T, f: F)
+    where
+        F: Fn(&mut T);
+
     /// Returns `true` if the binary search tree contains an element with the given value.
     fn contains(&self, value: &T) -> bool;
 
diff --git a/src/node.rs b/src/node.rs
index 0241cb7..bfc2f78 100644
--- a/src/node.rs
+++ b/src/node.rs
@@ -32,6 +32,24 @@ impl<T: Ord> Node<T> {
         Ok(())
     }
 
+    pub(crate) fn iterative_insert_or_update<F>(mut root: &mut HeapNode<T>, value: T, f: F) -> Result<bool, ()>
+    where
+        F: Fn(&mut T),
+    {
+        while let Some(ref mut node) = root {
+            match value.cmp(&node.value) {
+                Ordering::Equal => {
+                    f(&mut node.value);
+                    return Ok(false);
+                }
+                Ordering::Less => root = &mut node.left,
+                Ordering::Greater => root = &mut node.right,
+            }
+        }
+        *root = Some(Box::new(Node::new(value)));
+        Ok(true)
+    }
+
     pub(crate) fn recursive_insert(&mut self, value: T) -> Result<(), ()> {
         match value.cmp(&self.value) {
             Ordering::Equal => Err(()),
@@ -52,6 +70,32 @@ impl<T: Ord> Node<T> {
         }
     }
 
+    pub(crate) fn recursive_insert_or_update<F>(&mut self, value: T, f: F) -> Result<bool, ()>
+    where
+        F: Fn(&mut T),
+    {
+        match value.cmp(&self.value) {
+            Ordering::Equal => {
+                f(&mut self.value);
+                Ok(false)
+            }
+            Ordering::Less => match self.left {
+                None => {
+                    self.left = Some(Box::from(Node::new(value)));
+                    Ok(true)
+                }
+                Some(ref mut node) => node.recursive_insert_or_update(value, f),
+            },
+            Ordering::Greater => match self.right {
+                None => {
+                    self.right = Some(Box::from(Node::new(value)));
+                    Ok(true)
+                }
+                Some(ref mut node) => node.recursive_insert_or_update(value, f),
+            },
+        }
+    }
+
     pub(crate) fn iterative_contains(mut root: &HeapNode<T>, value: &T) -> bool {
         while let Some(current) = root {
             match value.cmp(&current.value) {
diff --git a/src/recursive.rs b/src/recursive.rs
index c92fb52..68d1088 100644
--- a/src/recursive.rs
+++ b/src/recursive.rs
@@ -2,8 +2,8 @@ use std::fmt::{Debug, Display, Formatter};
 use std::vec::IntoIter;
 
 use crate::BinarySearchTree;
-use crate::Node;
 use crate::HeapNode;
+use crate::Node;
 /// Recursive Binary Search Tree implementation.
 ///
 /// # Important
@@ -193,6 +193,47 @@ impl<T: Ord> BinarySearchTree<T> for RecursiveBST<T> {
         }
     }
 
+    /// Inserts the given value as a node or updates an existing node with the same value.
+    ///
+    /// If a node with the given value already exists, the provided function `f` is called
+    /// with a mutable reference to the existing value to update it.
+    ///
+    /// # Example
+    ///
+    /// ```rust
+    /// use bst_rs::{BinarySearchTree, RecursiveBST};
+    ///
+    /// let mut bst = RecursiveBST::new();
+    ///
+    /// bst.insert((1, 10));
+    /// assert_eq!(bst.retrieve(&(1, 10)), Some(&(1, 10)));
+    ///
+    /// bst.insert_or_update((1, 10), |tuple| tuple.1 = 30);
+    /// assert_eq!(bst.retrieve(&(1, 10)), None);
+    /// assert_eq!(bst.retrieve(&(1, 30)), Some(&(1, 30)));
+    ///
+    /// bst.insert_or_update((2, 20), |_| {});
+    /// assert_eq!(bst.size(), 2);
+    /// ```
+    fn insert_or_update<F>(&mut self, value: T, f: F)
+    where
+        F: Fn(&mut T),
+    {
+        match self.root {
+            None => {
+                self.root = Some(Box::from(Node::new(value)));
+                self.size += 1;
+            }
+            Some(ref mut node) => {
+                if let Ok(inserted) = node.recursive_insert_or_update(value, f) {
+                    if inserted {
+                        self.size += 1;
+                    }
+                }
+            }
+        }
+    }
+
     /// Returns `true` if the binary search tree contains an element with the given value.
     ///
     /// # Example
@@ -1652,4 +1693,30 @@ mod tests {
 
         assert_eq!(actual_bst, expected_bst);
     }
+
+    #[test]
+    fn successfully_insert_or_update_elements() {
+        let mut bst = RecursiveBST::new();
+
+        bst.insert((1, 10));
+        bst.insert((2, 20));
+        bst.insert((3, 30));
+        assert_eq!(bst.size(), 3);
+
+        bst.insert_or_update((1, 50), |pair| pair.1 = 15);
+        assert_eq!(bst.retrieve(&(1, 50)), Some(&(1, 50)));
+        bst.insert_or_update((1, 50), |pair| pair.1 = 15);
+        assert_eq!(bst.retrieve(&(1, 50)), None);
+        println!("{}", bst);
+        assert_eq!(bst.size(), 4);
+
+        bst.insert_or_update((4, 40), |_| {});
+        assert_eq!(bst.size(), 5);
+
+        bst.insert_or_update((4, 40), |pair| {
+            pair.1 *= 2;
+        });
+        assert_eq!(bst.retrieve(&(4, 40)), None);
+        assert_eq!(bst.retrieve(&(4, 80)), Some(&(4, 80)));
+    }
 }